The present invention relates to a pump unit for pressurising a hydraulic actuating system, in particular for an automotive appliance, more in particular for actuating a convertible roof system or a vehicle wheel suspension. The pump unit comprises a pump housing including a pump chamber for housing a piston pump. The piston pump comprises a pump stator which is stationarily positioned inside the pump chamber. The pump stator has a longitudinal pump stator body which defines an axial axis of the pump unit. The pump stator body includes at least two channels which respectively serve as an inlet or outlet channel. The piston pump further comprises a pump rotor. The pump rotor is positioned around the pump stator. The pump rotor has a pump rotor body which is driveable in a rotational direction about the axial axis. The pump rotor body includes several cylinder holes for receiving pistons. The pistons are radially slidable with respect to the pump rotor body.
Further, the piston pump comprises an eccentric ring for determining a pump capacity. The eccentric ring is positioned around the pump rotor body. The eccentric ring is eccentrically positioned with respect to the pump rotor body to provide an eccentricity in between an outer circumference rotor surface of the pump rotor body and an inner running surface of the eccentric ring.
U.S. Pat. No. 6,168,393 in the name of Hoerbiger discloses a conventional motor-driven radial piston pump assembly. The pump assembly is configured for transportable purposes or for generating small forces, for example, for the hydraulic activation of motor vehicle folding canopy tops. The main requirement to this pump assembly is that the assembly is as small as possible, such that the pump assembly can be built into narrow mounting spaces, e.g. into a narrow chassis compartment of a vehicle.
The pump assembly includes a radial piston pump which is supported by a base section on one side thereof. The base section serves to mount the pump together with all its connection lines, a control element and an electric motor. The electric motor is operatively connected to the pump and is supported on the base section coaxially with respect to a central axis of a motor output shaft which lies along a pump propulsion axis.
The electric motor is typically a conventional DC motor which functions to operate the pump. The electric motor comprises a motor housing which can be closed by a cover. The motor housing houses the motor. The motor is supported at a pump end and an opposite end. The motor has an output motor shaft at its pump end. Electrical components are provided at the opposite end. The output motor shaft is connected by a coupling to a rotor of the pump. The coupling comprises a flange shaped body and a beam shaped the link.
The electric motor is connected to the base section by the motor housing, so that all supporting, bearing forces and moments are carried by the base section. The base section can be constructed for the attachment of the entire motor-driven radial piston pump assembly. The base section bears the reaction forces and the weight of the motor and transmits those forces directly on the base section which also supports the pump which effects in a compact construction.
A drawback to this known pump assembly is that its outer size is still not small enough. A pump assembly of this type having small outer dimensions is highly desired.
GB 812.812A discloses a pump which comprises a housing for a stator, a rotor with pistons and a movable track ring. The rotor and track ring are arranged in a cylindrical recess of the housing. The rotor has a rotor shaft which is received in bores which are provided with anti-friction bearings, for example of the needle roller type on which the rotor shaft revolves. At its outer end, the rotor shaft is further supported by an additional anti-friction bearing. The rotor can be driven by coupling a motor onto the outer end of the motor shaft.
A drawback of this pump is that the pump capacity is limited. Further, the pump requires too much build-in space for use in an automotive actuating system.
EP 0 544.856 discloses a pump unit including a hydraulic piston pump driven by an electric motor. The piston pump and electric motor are housed in a common cylindrical pump housing which is at both ends closed by lid shaped components. The electric motor and piston pump form a first and second module which are coupled to each other.
The electric motor comprises a motor rotor. The motor rotor supports several magnets at its outer circumference. At one side, the motor rotor is journaled by a ball bearing to a shaft and at an opposite side, the motor rotor is supported by the piston pump. The motor rotor is driveable by actuating radially positioned coils opposite the magnets. The motor rotor is rotationally connected to a pump rotor of the piston pump, such that the pump rotor rotates together with the motor rotor.
The piston pump has a pump rotor body which is supported by a pump stator. The pump stator has an elongated stator body which is at one end fixed to the pump housing. The pump rotor body has a protrusion which is received in a recess of the motor rotor body. The pump rotor body is rotationally fixed to the motor rotor.
A drawback of the disclosed pump unit is that its outer size is still not small enough. A more compact pump unit is desired.
A further drawback is that the disclosed pump unit has a poor dynamic performance. Particularly, when driving such a pump unit at a high rotational speed and in an arbitrary orientation as it is desired in automotive appliances, such a pump unit will become unstable.
The general object of the present invention is to at least partially eliminate the above mentioned drawbacks and/or to provide a useable alternative. More specifically, it is an object of the invention to provide a pump unit which has a compact configuration and additionally provides stable dynamic behaviour when operating at a high rotational speed as it is required in automotive appliances, like operating a convertible roof system.
More in particular, the invention aims to provide a hydraulic actuating system including a compact pump unit which can be built-in into narrow mounting spaces, like a chassis compartment of a vehicle. Additionally, it is a further object to provide a pump unit which has a high dynamic performance which allows a build-in of the pump unit in an arbitrary orientation.
According to a first aspect of the invention, this object is achieved by a pump unit according to claim 1.